The present invention relates to an internal combustion engine having a valve characteristic control mechanism for altering operational characteristic of at least one of a suction valve and an exhaust valve driven by a cam provided on a camshaft, and a control valve for controlling pressure of working oil to be supplied to the valve characteristic control mechanism. Particularly, the present invention relates to an enclosure chamber in the internal combustion engine which encloses an endless flexible member such as chain or belt laid between the camshaft and a crankshaft for transmitting torque of the crankshaft to the camshaft to drive the camshaft.
Hitherto, an internal combustion engine having a valve characteristic control mechanism for altering operational characteristic of at least one of a suction valve and an exhaust valve driven by a cam provided on a camshaft supported on a cylinder head so as to rotate, and a control valve for controlling pressure of working oil to be supplied to the valve characteristic control mechanism has been known (Japanese Laid-Open Patent Publication No. 10-89023).
In this internal combustion engine, the control valve is constituted by an electro-magnetic solenoid valve and attached on a side surface of the cylinder head. Therefore, the control valve liable to be heated by electric current is cooled by the air to prevent excessive temperature rise, and since the control valve is positioned at a place not exposed to oil, an oil-proof control valve is unnecessary.
On the one hand, an internal combustion engine having an enclosure chamber for an endless flexible member such as chain or belt laid between the camshaft and the crankshaft to drive the camshaft by torque of the crankshaft which is formed by a case formed by an engine main body and a cover covering the case has been known.
In the internal combustion engine described in the above-mentioned Japanese publication, the control valve is projected from a side surface of the cylinder head, therefore arrangement of parts in the vicinity is restrained in order to avoid interference with the parts, and there is a room for improvement from a viewpoint of compactness of the engine. Further, the control valve is apt to vibrate owing to vibration transmitted from the cylinder head to exert a bad influence on operational performance of the control valve. Therefore, a control valve which is coped with the vibration and expensive must be used to cause high cost.
On the one hand, in the customary enclosure chamber, the cover vibrates owing to vibration transmitted from the engine main body and noise is generated.